Andrew Johnstone came across an interesting problem when he tried to use memcached multigets with a large number of keys - it was throwing failures, but only when he tried it on Ubuntu.

I Spent a little while yesterday investigating why memcached causes problems with multigets returning results and ended up comparing debian vs ubuntu. [...] A larger number of keys than 200 causes memcached to fail to return valid responses, additionally the key length greatly varies the number items you can pull back within a single multiget on Ubuntu, Debian implementation of memcached is able to handle all requests regardless of key length size.

He includes the code for his brief test and the output of the test runs on both Ubuntu and Debian systems. They clearly show the failures on the Ubunut side, with it throwing errors about "memcached_oi_read" and a zero length value returned to recv().